天然土壤对BDE-47的吸附特征

研究了BDE-47在3种不同有机质含量的天然土壤上的吸附行为,包括吸附过程动力学和热力学等温线。结果表明,双室一级动力学模式较单室一级动力学模式更适于描述BDE-47在天然土壤上的吸附过程动力学特征,尤其是在吸附初始阶段（0-49h）。快吸附在自吸附初始到表观吸附平衡的整体吸附过程中占据优势地位,而慢吸附的贡献率则逐渐增加并在97h后达到相对稳定。快吸附达到其吸附容量的时间远快于慢吸附。在吸附开始阶段的3~5h,BDE-47吸附总量的增加主要决定于快吸附,但在后续的吸附阶段,慢吸附的影响逐渐成为主导。因BDE-47水相溶解度很低,在较窄的平衡浓度范围内,线性分配模式和非线性Freundlich模式对BDE-47的吸附等温线都能提供很好的拟合结果。在Freundlich模型结果中,具有较低（0.72%）和较高（7.90%）TOC分数的土样的非线性指数n都明显低于1.0（分别为0.75±0.03和0.74±0.02）,表明2种土样在相应的BDE-47平衡浓度范围内表现出一定的非线性吸附特征;而另一TOC分数居中（2.86%）的土样则表现出显著的线性行为,其非线性指数n明显接近1.0（1.03±0.03）。

Sorption Characteristics of BDE-47 on Natural Soils

The sorption kinetic and isothermal behaviors of BDE-47 on three natural soils with different soil organic matter fractions（fOC） were studied. The results demonstrated that a two（fast and slow）-compartment first-order model was more appropriate for describing the sorption kinetic data, compared to a one-compartment first-order model, especially in the initial sorption stage within 49 h. The fast sorption was dominant during the whole sorption process from beginning to the apparent sorption equilibrium; while the contribution of the slow sorption to the total sorption amount gradually increased over time and then attained to a plateau at 97 h. The achieving time to the individual sorption capacity for the fast sorption was much shorter than that for the slow sorption. The contribution of the fast sorption to the increase in the total sorption amount of BDE-47 was prevailing at the start of sorption process from 3 h to 5 h; while the fraction of the slow sorption became principal in the subsequent stage of sorption process. Within the narrow equilibrium concentration range due to the fairly low aqueous solubility of BDE-47, the fitting results by the linear partitioning model were comparable with the linear portion by the nonlinear Freundlich model in this study. As for the Freundlich model, the nonlinear exponent（n） values of BDE-47 for the two samples with lower fOC（0.72%） or higher fOC（7.90%） were obviously lower than 1.0（0.75±0.03 and 0.74±0.02, respectively）, suggesting somewhat nonlinear sorption characteristics in the studied range of apparent equilibrium concentrations of BDE-47; whereas the linear behavior of BDE-47 for the left sample with medium fOC（2.86%） was indicated by its n value much closed to 1.0（1.03±0.03）.